Afterburner spraybars for jet engines are well appreciated assemblies by those persons skilled in the relevant art. An example of such spraybars is found in International Publication Number WO 2004/033966 A1 which designates the United States, and in the corresponding United States Provisional Patent Application having Application No. 60/319,601; each of which are hereby expressly incorporated by reference for purposes of disclosure.
In general, afterburner fuel spray arrangements are utilized to boost the thrust of jet engines during limited high-demand periods. Relevant to aircraft engines, such times can include, for instance, take off from the flight deck of an aircraft carrier.
The afterburner spraybars are located in the core gas flow of the jet engine, and are therefore subjected to extremely high temperatures, which can also be quite variable. This can present challenges, especially to configurations such as that shown in WO 2004/033966 A1 in which fuel pipes are directly exposed to the hot core gases behind the turbine section of the engine. Another problem with such fuel-pipe-exposed configurations is that the unsupported, relatively long length of the fuel pipes can make the assembly susceptible to eigenfrequencies (natural or harmonic frequencies) falling within engine range frequencies which is also viewed as detrimental.
For these reasons, it is generally known to provide protective heat shield structures for such afterburner fuel pipes, and even to distribute cooling bypass air thereto. One particular example is found in U.S. Pat. No. 5,297,391 wherein a fuel distributing pipe 52 is preceded (with respect to core gas flow) by a shielding tubular enclosure 54. Through the illustrations of FIGS. 4-6 of the '391 patent, however, it is clear that the overall length of the fuel pipe 52 remains substantially unbraced with regard to the enclosure 54. In fact, as depicted in FIG. 5 of the '391 patent, it is clear that a slit 70 must be maintained therebetween in order for cooling air to pass therethrough. Even though it could be said that it appears from FIG. 6 that a distal or bottom end of the fuel pipe could be anchored in a wall end 66 of the enclosure 54, it is not represented that the predominantly unsupported length of the fuel pipe 52 is braced against assuming harmonic oscillation, with the engine. This detrimental performance can obviously cause extreme vibration of the fuel pipe 52 and/or enclosure 54 resulting in unacceptable vibrations of, and friction and wear between, the several constituent components. Still further, each fuel pipe is individually enclosed, and no fuel pipes are arranged adjacent or abreast to one another in a crosswise orientation to the engine's core gas flow as defined by the present invention, and as will be described in greater detail hereinbelow. These individual assemblies disclosed in the '391 patent are not only costly, but their required frequency of radial distribution within the core gas flow can compromise the throughput of the engine.
For these reasons, as well as others that will become evident to those persons skilled in the art from the descriptive disclosure provided herein, the present invention has been developed to address these problems and provide additional benefits to users.